The specific aims of this proposal are: (1) To microdissect single human senile cortical cataractous lenses and to separate, with the aid of a microscope, opaque areas and adjacent normal areas. The cataractous and normal lens sections will be homogenized. The soluble structural lens proteins will then be separated by gel filtration with the aid of a high pressure liquid chromatography system. The separated crystallin fractions (Alpha, Beta, and Gramma-crystallins) will then be analyzed by various biochemical techniques which include: a. SDS-polyacrylamide gel electrophoresis and isoelectric focusing; b. Amino acid analysis; c. Tryptic peptide mapping of radioiodinated protein fractions employing the two-dimensional system of electrophoresis and chromatography followed by autoradiography; d. Non-tryptophan fluorescence properties of each protein fraction. The same technique will be applied to water-insoluble material from the microdissected lens sections. Denaturing agents and detergents will be used for solubilization. (2) To microdissect single human cortical cataractous lenses in which the opacities are caused by prolonged use of corticosteroids and lenses which have become opaque as the result of a secondary effect of retinitis pigmentosa. Normal and cataractous areas from these lenses will be subjected to biochemical analysis as described in (1). (3) To compare and analyze the major non-protein low molecular weight constituents in the opaque and clear lens sections isolated in (1) and (2). This will include determining the levels of glutathione, ascorbic acid, and carbohydrates. The fundamental questions which we will try to answer in this proposal are: (i) Which of the major lens structural proteins is involved or is affected in senile cortical cataractogenisis? (ii) Are the same proteins being affected in different opaque areas of the same lens? (iii) Are the same proteins involved in senile cataractogenesis in different lenses? (iv) Are there cases in which only the low molecular weight non-protein constituents are responsible for the opacity? (v) Which proteins are affected in the case where cataract is caused by a specific drug treatment, and which proteins are affected when cataract is caused by disease such as retinitis pigmentosa?